Microheterogeneous media

For the remainder of this chapter, we discuss results for various studies of interfacial solvation dynamics. We first discuss studies at liquid liquid interfaces at planar interfaces and in microheterogeneous media in Section II. In Section III, we discuss solvation dynamics at liquid solid interfaces. In Section IV, we review theoretical models and simulations of solvation dynamics at liquid interfaces. Finally, we conclude with a discussion of future studies. 

Dynamics of polar solvation have been studied at a range of differing liquid-liquid interfaces. These include planar liquid-liquid, and liquid-air interfaces as well as those found in microheterogeneous media. We discuss each case separately. 

Chen H, Farahat MS, Law KY, Whitten DG (1996) Aggregation of surfactant squaraine dyes in aqueous solution and microheterogeneous media correlation of aggregation behavior with molecular structure. J Am Chem Soc 118 2584-2594... 

The choice of method depends on the system to be investigated. The methods of intermolecular quenching and intermolecular excimer formation are not recommended for probing fluidity of microheterogeneous media because of possible perturbation of the translational diffusion process. The methods of intramolecular excimer formation and molecular rotors are convenient and rapid, but the time-resolved fluorescence polarization technique provides much more detailed information, including the order of an anisotropic medium. 

Reverse micelles are microheterogenous media where solubilized enzyme molecules are subject to the partitioning between different phases. The enzyme distribution between the phases is given by [183]... 

A. M. Braun and E. Oliveros, Local Concentrations Effects on Oxidation Reactions in Microheterogeneous Media, in Frontiers in Supramolecular Organic Chemistry and Photochemistry, H.-J. Schneider and H. Durr, Eds., VCH Verlagsgesellschaft, Weinheim, 1991, p. 393. 

Photochemical and Thermal Reactions of Hydrophobic and Surfactant Stilbenes in Microheterogeneous Media... 

The reactivity of molecules bound to surfaces, located at various kinds of interfaces, solubilized in microheterogeneous media, or incorporated as "guests" in various "hosts" as inclusion complexes has been the subject of much recent study. Indeed the structure of the medium, the nature of "solubilization sites" and reactivity in these environments have all been the focus of independent or interrelated investigations (1-12). Photochemistry has played a major role in these studies both in terms of studies of the media and also in terms of modified or controlled reactivity (1,5,8,9). In the course of these investigations numerous questions have arisen many of these have developed from differing pictures of solute-environment interactions which are furnished by different studies using different molecules as "probes" (5,10-12). Controversies arising... 

Studies presented here show that the various stilbene probes we have prepared and examined in different microheterogeneous media show a... 

What is the structure and the dynamics of hydrated/solvated electron in hot/supercritical water In dispersed clusters of polar liquids in nonpolar liquids In microheterogeneous media (e.g. water clusters in zeolite cavities) In mixed and complex solvents of practical importance (e.g. Ref. 107) on surfaces ... 

In classical, continuum theories of diffusion-reaction processes based on a Fickian parabolic partial differential equation of the form, Eq. (4.1), specification of the Laplacian operator is required. Although this specification is immediate for spaces of integral dimension, it is less straightforward for spaces of intermediate or fractal dimension [47,55,56]. As examples of problems in chemical kinetics where the relevance of an approach based on Eq. (4.1) is open to question, one can cite the avalanche of work reported over the past two decades on diffusion-reaction processes in microheterogeneous media, as exemplified by the compartmentalized systems such as zeolites, clays and organized molecular assemblies such as micelles and vesicles (see below). In these systems, the (local) dimension of the diffusion space is often not clearly defined. 

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